1. Field of the Invention
The present invention relates to an inexpensive, small zoom lens having a zoom ratio on the order of three, and an imaging device provided with the zoom lens.
2. Description of the Related Art
Digital still cameras, i.e., imaging devices provided with a solid-state image sensor, have come into wide use in recent years. The wide spread of digital still cameras is accompanied by demand for the further improvement of picture quality. Digital still cameras provided with a solid-state image sensor having a large number of picture elements need a photographic lens, particularly, a zoom lens, having an excellent focusing ability suitable for use in combination with the solid-state image sensor having a large number of picture elements. There has been strong demand for the miniaturization and const reduction of lenses, and the development of inexpensive, small, high-performance zoom lenses.
A zoom lens having a focusing ability suitable for use in combination with a solid-sate image sensor having a large number of picture elements is disclosed in JP-A No. 2002-350726. This known zoom lens is a three-lens-group zoom lens having a negative first lens group, a positive second lens group and a positive third lens group arranged in that order from the object side toward the image side.
Such a zoom lens is long as compared with its focal length and the lens groups are not satisfactorily miniaturized. Therefore, this lens cannot be collapsed in a satisfactorily small size. Since the interval between the first lens group and the second lens group is not optimized, there is a difficulty in forming the zoom lens in a short length, and the second lens group is inevitably large because an aperture stop is disposed between the lenses of the second lens group. The large second lens group makes collapsing the zoom lens in a small size difficult. Moreover, it is difficult to reduce the cost of this zoom lens.